Mixed and mixing layer depths simulated by an OGCM

Noh, Yign; Lee, Woo Sung

doi:10.1007/s10872-008-0017-1

Cited by 24 publications

(30 citation statements)

References 20 publications

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“…Positive discrepancies can also be seen in the Arabian Sea and Bay of Bengal for all the renalyses except G2V3 and ECCO-v4. In addition, in many reanalyses, negative discrepancies are seen in the Southern Ocean (in austral summer) such as reported in several studies (e.g., Gnanadesikan et al 2006;Noh and Lee 2008). Note that MLDs become larger from ORAS4 to ORAP5 in this region probably by incorporating the effects of the wave breaking and Langmuir circulation (Janssen 2012), although other updates of the system (e.g., horizontal resolution) may also have a contribution.…”

Section: Seasonal and Interannual Variations Of Mldsmentioning

confidence: 55%

“…In fact, larger MLDs are estimated from the averaged profiles than from the individual profiles, in particular with larger criteria, at high latitudes in winter. There, the averaging of the profiles with a relatively weak thermocline results in a weak thermocline being represented in the syntheses, leading to an overestimation of MLD/ILD, as indicated by Noh and Lee (2008). Here, the estimation error, e, is determined by using level spacing, Δz, relative position of the bending point of the profile to the grid, r, and vertical density gradient of the seasonal thermocline, ∂ρ ∂z , as where c is the lower limit of r, and is given by the relation that the density at a grid point is larger than the reference (10-m) value by Δρ exactly.…”

Section: Effect Of Vertical Resolutionmentioning

confidence: 99%

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Intercomparison and validation of the mixed layer depth fields of global ocean syntheses

et al. 2015

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5-7 (14-16) m with the vertical resolution of 25 (50) m when the criterion of potential density exceeding the 10-m value by 0.03 kg m −3 is used for the MLD estimation. Using the larger criterion (0.125 kg m −3 ) generally reduces the underestimations. In addition, positive biases greater than 100 m are found in wintertime subpolar regions when MLD criteria based on temperature are used. Biases of the reanalyses are due to both model errors and errors related to differences between the assimilation methods. The result shows that these errors are partially cancelled out through the ensemble averaging. Moreover, the bias in the ensemble mean field of the reanalyses is smaller than in the observation-only analyses. This is largely attributed to comparably higher resolutions of the reanalyses. The robust reproduction of both the seasonal cycle and interannual Abstract Intercomparison and evaluation of the global ocean surface mixed layer depth (MLD) fields estimated from a suite of major ocean syntheses are conducted. Compared with the reference MLDs calculated from individual profiles, MLDs calculated from monthly mean and gridded profiles show negative biases of 10-20 m in early spring related to the re-stratification process of relatively deep mixed layers. Vertical resolution of profiles also influences the MLD estimation. MLDs are underestimated by approximately This paper is a contribution to the special issue on Ocean estimation from an ensemble of global ocean reanalyses consisting of papers from the Ocean Reanalyses Intercomparsion Project (ORAIP), coordinated by CLIVAR-GSOP and GODAE OceanView. The special issue also contains specific studies using single reanalysis systems.

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Section: Seasonal and Interannual Variations Of Mldsmentioning

confidence: 55%

Section: Effect Of Vertical Resolutionmentioning

confidence: 99%

Intercomparison and validation of the mixed layer depth fields of global ocean syntheses

et al. 2015

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“…Many studies have reported the distribution of MLD in the global ocean with seasonal and interannual variations based on various sources of observational data and model results [ Kara et al ., ; de Boyer Montégut et al ., ; Carton et al ., ; Noh and Lee , ; Ohno et al ., ]. By and large, these studies focused on the winter mixed layer, in which the variation of MLD is large.…”

Section: Introductionmentioning

confidence: 97%

Seasonal variation of the upper ocean responding to surface heating in the North Pacific

et al. 2015

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Seasonal variations of the upper ocean, such as mixed layer depth (MLD) and sea surface temperature (SST), responding to the atmospheric forcing in the North Pacific (10°N–50°N), are investigated by analyzing the Argo and NCEP/NCAR reanalysis 1 data. The OAFlux data are also used for comparison. During the early heating period in the high‐latitude ocean north of 30°N, where a seasonal thermocline is formed above the deep mixed layer under strong surface heating, the MLD h is found to be scaled as h∝(Lλ)1/2, where L is the Monin‐Obukhov length scale and λ is the Ekman length scale. On the other hand, in the low‐latitude ocean south of 30°N, where the preexisting MLD is shallow and surface heating is weak, h is found to be scaled by λ. It is found that a large amount of heat flux across the MLD occurs, especially in the high‐latitude ocean during the late heating period, in which h is small. It suggests the contribution by turbulent mixing across the MLD in addition to radiation penetration, and the eddy diffusivity in the high‐latitude ocean is estimated as Kv ∼ 10−4−10−3 m2 s−1. The heat budget of the mixed layer reveals that the contribution from the ocean heat transport is much smaller than the surface heat flux in the high‐latitude ocean except in the Kuroshio region, but it is sometimes comparable in the low‐latitude ocean.

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“…Climatologies represent binned and averaged monthly fields. The z mix climatologies by Monterey and Levitus (1997); Kara et al (2003) by 0.03 kg m^-3 by 0.125 kg m^-3 subjective Fig. 4.…”

Section: Comparison With Density-and Temperature-based Z MIX and Climmentioning

confidence: 99%

“…Difference-based criteria perform better in such circumstances as well as in regions with temperature inversions or weak upper water column stratification. However, simulations using an ocean general circulation model have shown that a latitude-dependent difference criterion may actually give the best results (Noh and Lee, 2008).…”

Section: K Castro-morales and J Kaiser: Using Dissolved Oxygen Concmentioning

confidence: 99%

Using dissolved oxygen concentrations to determine mixed layer depths in the Bellingshausen Sea

Castro-Morales

Kaiser

2012

Ocean Sci.

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Abstract. Concentrations of oxygen (O 2) and other dissolved gases in the oceanic mixed layer are often used to calculate air-sea gas exchange fluxes. The mixed layer depth (z mix ) may be defined using criteria based on temperature or density differences to a reference depth near the ocean surface. However, temperature criteria fail in regions with strong haloclines such as the Southern Ocean where heat, freshwater and momentum fluxes interact to establish mixed layers. Moreover, the time scales of airsea exchange differ for gases and heat, so that z mix defined using oxygen may be different than z mix defined using temperature or density. Here, we propose to define an O 2 -based mixed layer depth, z mix (O 2 ), as the depth where the relative difference between the O 2 concentration and a reference value at a depth equivalent to 10 dbar equals 0.5 %. This definition was established by analysis of O 2 profiles from the Bellingshausen Sea (west of the Antarctic Peninsula) and corroborated by visual inspection. Comparisons of z mix (O 2 ) with z mix based on potential temperature differences, i.e., z mix (0.2 • C) and z mix (0.5 • C), and potential density differences, i.e., z mix (0.03 kg m −3 ) and z mix (0.125 kg m −3 ), showed that z mix (O 2 ) closely follows z mix (0.03 kg m −3 ). Further comparisons with published z mix climatologies and z mix derived from World Ocean Atlas 2005 data were also performed. To establish z mix for use with biological production estimates in the absence of O 2 profiles, we suggest using z mix (0.03 kg m −3 ), which is also the basis for the climatology by de Boyer Montégut et al. (2004).

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Mixed and mixing layer depths simulated by an OGCM

Cited by 24 publications

References 20 publications

Intercomparison and validation of the mixed layer depth fields of global ocean syntheses

Intercomparison and validation of the mixed layer depth fields of global ocean syntheses

Seasonal variation of the upper ocean responding to surface heating in the North Pacific

Using dissolved oxygen concentrations to determine mixed layer depths in the Bellingshausen Sea

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